Project Summary: The South African HIV epidemic continues to cause catastrophic human suffering across all sectors of society. With the rollout of antiretroviral therapy, however, far more South Africans are being tested for HIV and far more are entering HIV clinical care. The proposed research involves development, implementation, and evaluation of a culturally-appropriate HIV prevention intervention, situated in the South African HIV clinical care context, and aimed at assisting South African PLWHA to reduce HIV transmission risk behavior. This intervention approach is based on the behavior change framework from the Options Project;an acceptable, feasible, and effective HIV prevention intervention, implemented in US HIV care settings, which significantly reduced HIV+ individuals'HIV transmission risk behavior. The overall objective of the proposed research is to create a culturally-appropriate, effective, and efficient intervention strategy that may be widely disseminated within the South African clinical care context, to aid in stemming the South African HIV epidemic. The proposed research design involves a cluster randomized controlled trial of the effectiveness of a counselor-driven HIV prevention intervention, delivered in the South African clinical care context, compared to a standard-of-care control, in reducing HIV transmission risk behavior and incident STI rates among South African PLWHA. Specific aims of the proposed investigation are to conduct formative research with South African PLWHA and South African HIV care personnel, to identify unique obstacles to HIV preventive behavior for South African PLWHA, and to identify ways of overcoming these obstacles, in a feasible and culturally-acceptable, clinical care-based intervention;to design, pilot test, refine, implement, and evaluate an intervention, to be delivered in the South African HIV care setting, to assist South African PLWHA to reduce HIV transmission risk behaviors and incident STI;and to utilize the standard of care control as a cohort for a longitudinal natural history study of HIV transmission risk behavior, STI incidence, and how health improvements associated with ARV treatment may be related to changes in HIV risk behavior among South African PLWHA. Relevance. The proposed research aims to develop an effective and readily disseminated intervention to improve individual and public health by preventing transmission of HIV to uninfected individuals, and acquisition of STI by HIV+ persons, in the context of the South African HIV epidemic.